Summary: On the Soul (page 3)

Book II

Aristotle concludes his examination of the traditional doctrines of his predecessors on the soul.

He now seeks to offer a positive definition: Let us endeavour to determine what the soul is and what may be its most general definition ¹.

For Aristotle, the soul is a substance. He recalls the ambiguous meaning of this notion, as he established it in other works such as the Physics: substance may refer to the matter of a thing, the form it takes, or even the compound of matter and form (all things ultimately being matter shaped into a certain form).

According to Aristotle, the soul is a substance in the second sense: it is form—the form of the body, which constitutes its matter. The union of the two constitutes the living being.

Thus, the soul is necessarily substance in the sense that it is the form of a natural body possessing life in potential ².

Moreover, form is act (or entelechy), whereas matter is potency (as Aristotle showed in the Metaphysics) the soul is therefore the entelechy of a body having life in potency ³.

Matter and form of a thing cannot be separated: There is no need to investigate whether the soul and the body are one, any more than there is for wax and its imprint ⁴. It is not the body or the soul that exists, but the body and the soul—or more precisely, the animated body.

Again, the soul is form or act of the body:

Therefore, it is with good reason that thinkers have held that the soul can be neither without a body nor a body itself, for it is not a body but something belonging to the body ⁵.

One could say that the "edge"—the cutting edge—is to the axe what the soul is to the body, or that the soul is to the body what sight is to the eye.

Aristotle reviews the various faculties of the soul, progressing from the lower to the higher: these are the nutritive, desiderative, sensory, locomotive, and dianoetic faculties.

Some beings (such as plants) possess only the nutritive faculty; others add touch or other senses; man develops the higher faculties.

Sensation is the foundation of animal organisation. Touch is the primary sense, for it primarily belongs to all animals, and without touch, no other sense can exist, whereas touch can exist without the others ⁶.

Through the nutritive faculty—the first and most universal of all faculties—life belongs to all beings: it encompasses both the assimilation of food and reproduction: The same faculty of the soul is both nutritive and generative ⁷.

Starting from an apparent paradox (why is there no sensation from the organs themselves?), Aristotle explains the mechanism of perception: the sensory faculty (e.g., sight) exists not in act but only in potency, and it is the perceived object that actualises it.

Sight is made possible by the diaphanous medium, which underlies all colour phenomena; composed of air and water, it is a transparent medium between the object and the eye.

Aristotle observes that we speak thanks to the larynx and that our sense of smell is less developed than that of most animals. On the other hand, by the delicacy of touch, man surpasses all other creatures. And that is why he is the most intelligent of animals ⁸. Taste is a kind of touch.

The general mechanism of sensation is as follows: The sense is the receptacle of sensory forms without matter, just as wax receives the impression of a ring without iron or gold ⁹.

¹ II, 1, 412a
² ibid.
³ ibid.
⁴ ibid., 412b
⁵ II,2, 414a
⁶ II, 3, 415a
⁷ II, 4, 416a
⁸ II, 9, 421a
⁹ II, 11, 424a